pigweed vs purslane

pigweed

noun
  • Polygonum aviculare (common knotgrass) 

  • Amaranthus species 

  • Portulaca bicolor, of Australia 

  • Heracleum sphondylium 

  • Any of various weedy plants sometimes used as pig fodder 

  • Chenopodium album, white goosefoot 

purslane

noun
  • purslane tree (Portulacaria afra) 

  • pink purslane (Claytonia sibirica) 

  • Halimione portulacoides 

  • moss-rose purslane, moss rose (Portulaca grandiflora) 

  • shoreline purslane (Sesuvium portulacastrum) 

  • Honckenya peploides 

  • winter purslane, miner's lettuce (Claytonia perfoliata) 

  • the widely-grown edible plant common purslane or summer purslane (Portulaca oleracea) 

  • Any of the family Portulacaceae (order Caryophyllales) of succulent plants. 

How often have the words pigweed and purslane occurred in a corpus of books? (source: Google Ngram Viewer )